JACKSON, Miss. - A Mississippi sheriff's department is refuting claims by the campaign of a challenger in a hotly contested Senate primary here that three staffers associated with the campaign were let into the Hinds County Courthouse in Jackson, Miss., by "uniformed personnel" sometime after election officials had closed the building and gone home from counting votes early Wednesday morning.

Hinds County Sheriff's Department spokesman Othor Cain said the incident is under investigation as officials try to figure out how Janis Lane, Scott Brewster and Rob Chambers entered the courthouse. They were inside until about 3:45 a.m., Cain said.

Brewster is a former coordinator of presidential candidate Newt Gingrich's Mississippi operation and is currently state Sen. Chris McDaniel's campaign coalition coordinator.

McDaniel is trying to unseat six-term Republican Sen. Thad Cochran.

Lane is a member of the Central Mississippi Tea Party and is a longtime supporter of McDaniel.

Chambers is a consultant with the Mississippi Baptist Christian Action Commission who has worked with McDaniel and members of the Senate Conservative Coalition to fight Common Core.

The courthouse was locked down when all elections personnel left around 11:30 p.m., Cain said.

"There are conflicting stories from the three of them, which began to raise the red flag, and we're trying to get to the bottom of it," Cain said Wednesday. "No official charges have been filed at this point, but we don't know where the investigation will lead us."

McDaniel campaign spokesman Noel Fritsch issued a statement late Wednesday saying the campaign "sent people to the Hinds courthouse to obtain the outstanding numbers and observe the count." The statement reiterated the people were allowed in by "uniformed personnel" and then being locked inside.

"Predictably, a close Cochran ally wants to make hay out of this. Sadly, the Cochran campaign wants to make this election about anything but issues. Mississippians deserve better than this sort of distraction politics," Fritsch said in the statement.

Hinds County Sheriff's Department does work security for the courthouse, but only during business hours, Cain said Thursday. During an election, off-duty deputies are hired by the elections commissioners to work security, but at the time Lane, Brewster, and Chambers allegedly gained access to the courthouse, all security would have been long gone.

"It's a fabrication that someone pointed them to a door. I think that's a total misrepresentation of fact," Cain said. "None of our guys let anybody in."

The sheriff's department has requested courthouse security footage.

Cain said Thursday that regardless of what the McDaniel campaign is saying, inconsistencies in statements given by Lane, Chambers and Brewster led to the opening of the investigation late Wednesday.

"It's important to note that Janis Lane's story and the other officials' stories continue to change through the investigation," he said. "They changed within five minutes, which caused us to be even more deliberate and determined to find out what was going on."

Brewster's name popped up during the first days after conservative political blogger Clayton Kelly was arrested and charged in a photo scandal involving Sen. Cochran's bedridden wife, Rose. Kelly was accused of sneaking into Rose Cochran's Madison, Miss., nursing home and taking photos of her for a political video.

After Kelly's arrest, three other McDaniel supporters were charged with conspiracy in connection with the nursing home case.

After The (Jackson, Miss.) Clarion-Ledger broke the news of Kelly's arrest, Brewster said he was aware of the video.

However, later after Brewster acknowledged the video, McDaniel and other campaign leaders said they knew nothing about the video.

Brewster couldn't be reached for comment Wednesday.

Cochran campaign spokesman Jordan Russell said Wednesday, "It is astonishing that the same people who are up to their eyeballs in four felons breaking into a nursing home are also up to their eyeballs in potentially breaking in somewhere else again."

"And this time they can't deny that a paid staffer is involved," Russell said. "At some point you got to say enough is enough. How many more arrests of allies and McDaniel team members before we can say this has gone too far?"

"The McDaniel campaign, they seem to always be on the wrong side of a door," said Barbour, a Republican who served as governor from 2004-2012. "Have you ever heard of a group of people who were in places they weren't supposed to be more often?"

Hinds County Republican Executive Chairman Pete Perry said he had serious concerns about the incident.

"I don't care who it is. I have a concern with someone being in the courthouse with all the election material down there," Perry said.

Perry said everyone left the courthouse by 11:30 p.m. Tuesday and locked up.

He said he got a phone call from Lane around 2 a.m. Wednesday saying two people, including her, were locked inside the courthouse and were looking for a way out.

Cain said there was never a threat to any ballots, which were already secured.

Perry said Lane was a precinct worker and had dropped off her ballot materials about 8:30 p.m. Perry said some precinct information wasn't sealed.

Hinds County Circuit Clerk Barbara Dunn said it would be virtually impossible to tamper with ballots after they make it to her office.

All ballots including absentee were locked inside a vault in her office, which was locked when everyone left Tuesday night between 11 p.m. and 11:30 p.m, Dunn said.

"It would be very hard for anyone to get into my vault," Dunn said. "And I have an alarm system that is turned on that would make a loud sound if anyone opens the vault."

The McDaniel-Cochran race is going to a June 24 runoff because a third candidate received a small share of Tuesday's primary vote, preventing either of them from receiving the majority needed to win.